Method for the treatment of cellulose and product resulting therefrom



Sept. 8, 1931. s. E. SEAMAN 1,322,174 METHOD FOR THE TREATMENT OFGELLULOE AND PRODUCT RESULTING THEREFROM Filed July 3, 6 2 Sheets-Sheet1 I7we71/t07 Siewa 56am an J aawwg 1,822,174 METHOD FOR THE TREATMENT OFCELLULOSE AND PRODUCT RESULTING THEREFROM.

Sept. 8, 1931. s. E. SEAMAN Filed July 3, 192 2 Sheets-Sheet 2 l i @i[7?)6'677/607 SiezuarZZZSeanz'an Q W MW, 51%

fiZZ i9 METHOD FOR THE TREATH manta Sept. 193i or nausea, MAINE,

Assrenon To nas'man nnmzrrnoronmo COMPANY, OF SOUTH BREWER, MAINE, ACORPORATION OF MASSACHUSETTS OF CELLULOSE AND PRODUCT RESULTING TEBOKApplication filed July 3, 1928. Serial No. 120,372.

' cial quantities) it hasheretofore been conconsidered, or some of thesidered as a standard and preferred raw material for the manufacture ofcellulosic derivatives such as nitrocelluloses and the like, in whichcontrol of the conversion reactions,

certainty of the final chemical composition and uniformity of physicalproperties of the resulting product are essential elements. However,when contrasted with the cost of other sources of cellulosic materials,cotton has been relatively expensive. Consequently, numerous effortshave been made to render such cheaper materials available for thepurpose of chemical conversion into various cell-ulosic derivatives. Inthis endeavor, wood has usually been the rimary source y products ofWood such as sawdust, or in a few instances cellulosic substances ofother derivation.

Without enumerating the various courses which such efforts have taken orthe measure of success or failure by which they have been ultimatelyattended, it is here sufiicient to state that in general they did notrecognize, or they disregarded those chemical and physicalchracteristics of cellulosic materials or fibres which facilitate or areessential to .the subsequent reactions required, leading to ments of t eprior art have not produced a suitable cellulose for purposes ofconverting it into its derivatives. v

In this connection it is to be observed that while cotton possesses thequalities above-set forth to recommend it for chemical treatment, theraw cotton fibre itself is not, in the first instance, susceptible to aready and uni-- removal of impurities, including a superficial 5 formconversion into cellulos1c derivatives. v

On the contrary, it requires the preliminary filmv consisting of a moreresistant Wax-like v substance which covers and efiectively protects thecellulosic body portion of the individual vfibre. Inorder to adequatelyefiect this removal, the cotton must be subjected to a suitabletreatment, sufficiently active to remove this outer waxy layer. In thecourse of such treatment, the inner cellulosic substance is unavoidablyreacted upon and, in

the use of aqueous solutions, is invariably changed. This will occur asa condition in: herent to such processes, even though the utfurtheraction by the reagents or by the mechanical treatments employed, beforeremoval of the wax-like coating has been accomplished.

- A similar condition is presented byother quently purified to thedegree desirable for.

esterification or like purposes.

It is to be observed and emphasized as an inherent part of the generalconcept of the present invention that, while the chemical condition ofthe cellulosic material to be reacted upon is of fundamental importance,the physical characteristics which are manifest in the esterificationprocess are equally as important if not in actual practice functionallymore controlling. For example, attention is directed to the specificqualifications, that in order for the esterifying reagent to reactuniformly upon the individual cellulosic fibres, it must come intointimate and uniform contact therewith. It must also 70 most precautionsand care are taken to avoid efiect such contact rapidly in order thatthe time of reaction upon all portions of the charge of the cellulosebase under treatment may be approximately the same. Otherwise, since thecomposition of the cellulosic deriva tive actually-produced (as with thenitrates) is a direct function of the time of reaction, those portionswhich are first brought into Contact with the esterifying agent may beover-converted, relative to those acted upon afterwards.

This would imply asubstantially instantaneous penetration of theesterifying reagent upon and into each and every portion and particle ofthe cellulosic material under treatment, lncidental'to such penetration,there is also involved the simultaneous displacement of entrainedvolumes of air or other gaseous inclusions, as well as the superficiallyadsorbed gaseous components which may be associated with the surfaces ofthe individual cellulosic fibres. Moreover, the reagent must also reachall. parts of the cellulosic substance in quantities sufiicient to bringabout the desired conversion.

In this aspect of the physical conditions of the esterii ying reaction,the course of the chemical reaction or reactions again becomespredominant, That is to say, upon the initial contact of the cellulosebody with the esteriiijying reagent, an apparent gelatinization may takeplace, inhibiting further penetration of reacting agents. lhis retardsor inhibits further penetration of the esterifying reagent into thecellulosic material and therefore ma not onl cause the formation ofsuccessive ayers o' cellulose structure characterized by successivelyreduced degrees of esterification from the outer surface to the centerbut may leave the central portions of the gall'ulose aggregatesentirely-unafiected there- It is therefore an object of this inventionto provide a mode or treatment for cellulosic material (other thancotton) for the purpose of reducing the same to both a physicalcondition and chemical state closely associated Withthe subsequentconversion of the same into esters or other derivatives, uniformly, andupon a commercial scale.- Further and more specific objects of theinvent tion will bemanifest from the following disclosure.

The rocedure involving the subject mat ter of tfi is invention includesin general terms a preliminary reduction of the cellulosic material fromthe condition in which it is usually found in nature to the condition ofa pulp, retainingsthe fibrous structure thereof so far as may consistentwith an adequate opening up of the raw material, removing the reagentsand other materials which are entrained in or associated with thecellulosic portion and may be regarded as impurities, putting the pulpthus produced nto any convenient form, a portion of the water beingremoved therefrom, then formin the fibrous mass into separatedaggregates o a predetermined order of size or sizes, (withoutsubstantially compacting or consolidating the same) and finally dryingthe resulting mass of fibrous cellulosio aggregates.

More specifically, the invention will be described in its relationshipto the preparation of wood cellulose by the sulfite process, resultingin a pulp of a relatively high degree of alpha cellulose. This isfollowed by a secend-stage treatment of the pulp generally characterizedby reagents (such as allraline solutions, with or without alkaline metalrcactive compounds of sulfur) efiective to remove further impuritieswithout appreciable detrimental action upon the cellulosic content, andfinally partially dehydrating the pulp and subjecting it preferably to asuccession of finely gauged and closely spaced picker teeth by which theindividual groups of fibres are caught and rent apart (withoutappreciable disruption of the fibres them selves) into small tufts oraggregates. These aggregates are more or less uniform in size or volumeand are characterized by a high alpha cellulose content andsubstantially free from resins and other reaction-inhibiting substances,in such condition as to facilitate penctration by the fibre-wettingliquids' without entrapped air or liberated gases of reaction to acommercially detrimental de reofi (The physical condition of theprocedure of engaging the fibres with er;- tremely fine points atsuitably spaced intervals and plucking the fibres engaged by one pointand those more or less firmly intertwined with them from those engagedby an adjacent point (and the fibres intertwined with them) withoutdestroying the length of individual fibres and at the same time withoutdetrimentally compacting such clusters of iibres together. It is,nevertheless, believed that the picking points do compact the fibresimmediately engaged thereby to a suificient extent to promote theinterlocking arrangement and to thereby create an integrity of theaggregate of fibres which in experience is found to be persistentlypreserved throughout such subsequent handling as may be necessary infibre form for baling, storage, etc.

He the ultimatesize or volume of such aggregates may be controlled andvaried at will, the number of fibres which each aggregate contains willnecessarily be varied. Hence, what. may be termed the fibre density ofthe separate tufts or aggregates produced by the present invention maybe correspondingly controlled and varied (in the maximum size) toaccommodate the product to specificr'equirements of the subsequentconversions to which it is to be subjected. In actual experience, forexample in nitratfibrous aggregates so produced may be attributed to theMill llllv lllli Mid ing the product with mixed acid, it has been vfound that when the aggregates are approximately of the size of mustardseed, weighing approximately 1 milligram or less and containingapproximately 40,000 fibres or less, a satisfactory nitration thereofmay be accomplished and a uniform and stable nitrated product isobtained.

A typical succession of steps leading to a product of the desiredchemical and physical characteristics with respect to asubsequentconversion, as to nitrocellulose will now be described, reference beinghad to the accompanying drawings, in-which:

Fig. 1 is a diagrammatic representation of a series of apparatus used,andto. be'considered as in the nature of a fiowsheet;

Fig. 2 is'a.side elevation more in detail of the picker element of theapparatus;

Fig. 3 is a front view of the picker teeth rollers; and i F ig. '4 is anenlargedview of the picker teeth'per se.

Referring now to Fig. 1' of the drawings, numeral 1 indicates the rawmaterial in convenient form, 2 a conveyor leading to the hopper ofshredder 3 which stands above the manhole 4 of rotary digester '5. Thelatter is mounted above the washing vat 6, disposed as to transfer thecharge from'5 to'vat 6. Tank 6 has an outlet shown at? into bleach tank8 from which conduit 9 leads through valve 11 and pump 12 to a thickener13. This may be of other form but is'shown as comprising screen roll 14andcouch roll 15, from'which the pulp may be delivered over chute 16 toconveyor 17 leading to squeeze rolls 18, followed by conveyor 21, 22,feed rolls 23, and picker 24. The latter may be of any desired type anddelivers through chute 26 to tower 28 h'aving latticework 29 o'r'similarretarding means "for catching the product delivered to it andpermittingit to fall on conveyor 31 leading to the picker 33.

The latter comprises a central drum 34 mounted for rotation on trunnions35 and having parallel and adjacent to the upper arc of its periphery aseries of smaller picker roll workers shown as 36, 37, 38, 39, 40, 41'and 42 conveniently spaced. The largerdrum or cylinder 34 (see Figs, 2and 3 is provided with teeth 43 properly formed along the margin of acontinuous metal strip 44 as shown in Fig. 4. This strip may be mountedin helical grooves in the surface of the cylinder 34, and firmlyseatedtherein and peened in position. The adjacent rows of teeth 45 maybe spaced apart by varying distances but are in any event relativelyclose together, as shown in Fig. '3 (by which satisfactory results havebeen obtained using 22 rows to the linear inch). The smaller pickerrolls 36 to 42 inclusive may be similarly provided with picker teeth 46in rows 47 spaced apart to correspond to the rows upon cylinder 34.

ample, the teeth upon the strips used in picker roll 36 maybe of theorder of 10 to the linear inch while those on succeeding rolls 37 to 42may be successively more closely spaced, so that the teeth on pickerroll 42 will be 26 or moreto the linear inch. Again, it should beunderstood that these rows or the teeth thereon maybe differentlyspaced,

53 toa chute 54 which in turn exists to' a baling or compressing chamber55 in which a piston 56 maybe slidably mounted and eccentricallyconnected by'driving rod 57 to the eccentric 58. The exit to the balingchamber may be at 59 from which the bales of compressed pulp may bewithdrawn.

' I11 operation the raw material may be pulp which has. been obtained bymethods now the usualbisulfile treatment, which is pref- 'erablydiminished in duration or in intensit of action or both to constitute araw cook or even somewhat less than what, for purpgses of paper making,would beregarded as a suitable raw cook,-then washed and subjected to ableachin treatment if desired. The-material (woo pulp 1 as obtainedabove) is fed onto the conveyor beltv2 by which it is delivered to theshredder 3. It is torn apart and discharged through the manhole 4 intodigester 5. Here it is treated with an alkaline solution preferablycontaining a reactive compound of sulfur, such as sodium sulfite. Thissolution may be of a concentration of approximately 3% by weight ofreagent materials, but preferably contains substantially equal parts ofthe caustic soda and of bisulfite (see copending application of C. A.Blodgett and H. H. Hanson, Serial N0.'87,806, filed February 12,

2. A process for-the preparation of cellulosic materials especiallysuitable for esterification purposes which comprises reducing Wood tothe condition of a fibrous pulp,'puri,- fying the same by removal ofimpurities contained therein, conducting and controlling said treatmentso as to alter the physical and chemical properties of the cellulose, toa condition adapted for rapid wetting of the same by esterifyingreagents, partially removing moisture, and forming the same into fibreaggregates of a predetermined order of size, by the operation ofpicking, and finally'drymg.-

3. A process for treating cellulose from wood, comprising purifying thesame with an alkaline solution, washing the thus treated pulp free fromextraneous materials, bleaching,'separating the bleaching liquortherefrom, removing excess water, passing the pulp thus obtained througha succession of picker rolls having teeth thereon closely spaced and inclosely arranged rows, to form cellulosic fiber aggregates ofapproximately one milligram in weight or less and containing anapproximate maximum of forty thousand individual fibers per aggregate,and finally drying.

4. A process for treating cellulose from wood, comprising purifying thesame with an alkaline solution containing sodium sulfite,

washing the thus treated pulp free from extraneous materials, bleaching,separating the bleaching liquor therefrom, removing excess water,passing the pulp thus obtained through a succession of picker rollshaving teeth thereon closely spaced and in closely arranged rows, toform cellulosic aggregates of approximately onemllhgram in weight orless and containing an approximate maximum of forty thousand individualfibers pe aggregate. and finally drying. v 5. A cellulosic productconsisting essentially of. separated, purified, independent woodcellulose fibers, characterized by being assembled into independentaggregates or clusters. the individualfibers of the same being ininterlocking engagement with each other and radiating therefrom in-mutually spaced relationship to form independent highly absorbentmasses.

6. An aggregate or cluster of purified, separated wood cellulose fibers,said fibers contacting with each other in interlocking engagement, andradiating freely in mutually spaced relationship therefrom to form ahighly absorbent mass.

7. An aggregate or cluster of purified, separated wood cellulose fibers,said fibers contacting with each other in interlocking engagement, andradiating freely in mutually spaced relationship therefrom to form ahighly absorbent mass, said aggregate or

